Effects of Low, Moderate, and High Intensity Exercise on Functional Impairment and ADHD Symptoms: A Randomized Pilot Study

Background: Exercise improves cognitive functions impaired in attention deficit/hyperactivity disorder (ADHD); however, most research involves children or animal models. Effects on adult ADHD symptoms and optimal exercise intensity remain unclear. Moderate and high intensity cycling show benefits. Purpose: We evaluated the feasibility of an exercise intervention and compared 3 levels of exercise intensity in college students with ADHD symptoms. Methods: In a randomized controlled trial, 33 participants were assigned to low, moderate, or high intensity exercise. All groups cycled for 20 minutes. The low and moderate intensity groups cycled at low or moderate intensity, respectively. The high intensity group alternated 20-second maximal effort bursts with 120 seconds of low-intensity cycling. The exercise occurred over 1 week. Outcomes were evaluated before and after the intervention. Results: There was a decrease in functional impairment ( F = 7.98, P = .009, partial η 2 = 0.222) and symptom severity ( F = 13.43, P = .001, partial η 2 = 0.324). There was no difference between groups. Inattentive symptoms responded to low intensity ( t = 2.62, P = .015, d = 0.874) and moderate intensity exercise ( t = 2.61, P = .013, d = 0.786). Impulsive symptoms benefited from low ( t = 4.06, P = .002, d = 1.35) and moderate intensity exercise ( t = 1.99, P = .037, d = 0.600). Hyperactive symptoms were reduced in the moderate intensity group ( t = 2.6, P = .013, d = 0.783). Conclusion: Feasibility was demonstrated. Moderate intensity exercise appears to be the most universally effective intensity for reducing ADHD symptoms. Study Registration: ClinicalTrials.gov, NCT06753253.